// less 嵌套
.header {
    width: 200px;
    height: 200px;
    background-color: pink;
    .logo {
      width: 100px;
      height: 100px;
      background-color: green;
    }
  }
  .nav {
    width: 200px;
    height: 200px;
    background-color: pink;
    a {
      display: block;
      width: 100px;
      height: 100px;
      background-color: skyblue;
      &.box {
        background-color: yellowgreen;
      }
      
    }
    a:hover {
        background-color: deeppink;
      }
    
  }